This invention relates to a wire printing head of ballistic type, comprising a plurality of wires slidable axially in a guide, and which are projected by the armatures of a corresponding plurality of control electromagnets in order to effect printing.
A head of this type is known in which a group of seven or nine electromagnets is supported by a semicircular metal plate disposed transversely to the printing wires. A resin block fixes the individual cores and the energising coils to the baseplate. Most of the radiating surface is therefore in resin, and this leads to considerable temperature rises in the most inner parts of the energising coils, especially when the number of electromagnets and/or their frequency of energisation are to be increased. This represents a serious limit to high speed printing.